1. Field of the Invention
The present invention relates generally to electronic protection circuitry. More specifically, the present invention relates to a field-effect transistor embedded with an electrically activated surface mount thermal fuse.
2. Introduction to the Invention
Protection circuits are often utilized in electronic circuits to isolate failed circuits from other circuits. For example, the protection circuit may be utilized to prevent a cascade failure of circuit modules in an electronic automotive engine controller or on a computer motherboard. Protection circuits may also be utilized to guard against more serious problems, such as a fire caused by a transistor overheating or other power supply circuit failures.
One type of protection circuit is a thermal fuse. U.S. Publication No. 2010/0245027, published Sep. 30, 2010, and U.S. Publication No. 2010/0245022, published Sep. 30, 2010, each of which is incorporated herein by reference in its entirety, disclose improved thermal fuses that are resettable, or reflowable. The reflowable thermal fuse is configured to, for example, open a circuit if a field-effect transistor (FET) temperature reaches an overtemperature condition. The reflowable thermal fuse may be placed close enough to the FET to provide sufficient heat transfer. The reliability of the reflowable thermal fuse to detect an overheating FET and open the corresponding circuit is improved by an increased proximity to the FET, which ensures a more efficient heat transfer from the FET to the reflowable thermal fuse.